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template_lapack_rscl.h
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1 /* Ergo, version 3.8, a program for linear scaling electronic structure
2  * calculations.
3  * Copyright (C) 2019 Elias Rudberg, Emanuel H. Rubensson, Pawel Salek,
4  * and Anastasia Kruchinina.
5  *
6  * This program is free software: you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License as published by
8  * the Free Software Foundation, either version 3 of the License, or
9  * (at your option) any later version.
10  *
11  * This program is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14  * GNU General Public License for more details.
15  *
16  * You should have received a copy of the GNU General Public License
17  * along with this program. If not, see <http://www.gnu.org/licenses/>.
18  *
19  * Primary academic reference:
20  * Ergo: An open-source program for linear-scaling electronic structure
21  * calculations,
22  * Elias Rudberg, Emanuel H. Rubensson, Pawel Salek, and Anastasia
23  * Kruchinina,
24  * SoftwareX 7, 107 (2018),
25  * <http://dx.doi.org/10.1016/j.softx.2018.03.005>
26  *
27  * For further information about Ergo, see <http://www.ergoscf.org>.
28  */
29 
30  /* This file belongs to the template_lapack part of the Ergo source
31  * code. The source files in the template_lapack directory are modified
32  * versions of files originally distributed as CLAPACK, see the
33  * Copyright/license notice in the file template_lapack/COPYING.
34  */
35 
36 
37 #ifndef TEMPLATE_LAPACK_RSCL_HEADER
38 #define TEMPLATE_LAPACK_RSCL_HEADER
39 
40 
41 template<class Treal>
42 int template_lapack_rscl(const integer *n, const Treal *sa, Treal *sx,
43  const integer *incx)
44 {
45 /* -- LAPACK auxiliary routine (version 3.0) --
46  Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
47  Courant Institute, Argonne National Lab, and Rice University
48  September 30, 1994
49 
50 
51  Purpose
52  =======
53 
54  DRSCL multiplies an n-element real vector x by the real scalar 1/a.
55  This is done without overflow or underflow as long as
56  the final result x/a does not overflow or underflow.
57 
58  Arguments
59  =========
60 
61  N (input) INTEGER
62  The number of components of the vector x.
63 
64  SA (input) DOUBLE PRECISION
65  The scalar a which is used to divide each component of x.
66  SA must be >= 0, or the subroutine will divide by zero.
67 
68  SX (input/output) DOUBLE PRECISION array, dimension
69  (1+(N-1)*abs(INCX))
70  The n-element vector x.
71 
72  INCX (input) INTEGER
73  The increment between successive values of the vector SX.
74  > 0: SX(1) = X(1) and SX(1+(i-1)*INCX) = x(i), 1< i<= n
75 
76  =====================================================================
77 
78 
79  Quick return if possible
80 
81  Parameter adjustments */
82  Treal cden;
83  logical done;
84  Treal cnum, cden1, cnum1;
85  Treal bignum, smlnum, mul;
86 
87  --sx;
88 
89  /* Function Body */
90  if (*n <= 0) {
91  return 0;
92  }
93 
94 /* Get machine parameters */
95 
96  smlnum = template_lapack_lamch("S", (Treal)0);
97  bignum = 1. / smlnum;
98  template_lapack_labad(&smlnum, &bignum);
99 
100 /* Initialize the denominator to SA and the numerator to 1. */
101 
102  cden = *sa;
103  cnum = 1.;
104 
105 L10:
106  cden1 = cden * smlnum;
107  cnum1 = cnum / bignum;
108  if (absMACRO(cden1) > absMACRO(cnum) && cnum != 0.) {
109 
110 /* Pre-multiply X by SMLNUM if CDEN is large compared to CNUM. */
111 
112  mul = smlnum;
113  done = FALSE_;
114  cden = cden1;
115  } else if (absMACRO(cnum1) > absMACRO(cden)) {
116 
117 /* Pre-multiply X by BIGNUM if CDEN is small compared to CNUM. */
118 
119  mul = bignum;
120  done = FALSE_;
121  cnum = cnum1;
122  } else {
123 
124 /* Multiply X by CNUM / CDEN and return. */
125 
126  mul = cnum / cden;
127  done = TRUE_;
128  }
129 
130 /* Scale the vector X by MUL */
131 
132  dscal_(n, &mul, &sx[1], incx);
133 
134  if (! done) {
135  goto L10;
136  }
137 
138  return 0;
139 
140 /* End of DRSCL */
141 
142 } /* drscl_ */
143 
144 #endif
template_lapack_lamch
Treal template_lapack_lamch(const char *cmach, Treal dummyReal)
Definition: template_lapack_lamch.h:202
absMACRO
#define absMACRO(x)
Definition: template_blas_common.h:47
dscal_
void dscal_(const int *n, const double *da, double *dx, const int *incx)
template_lapack_rscl
int template_lapack_rscl(const integer *n, const Treal *sa, Treal *sx, const integer *incx)
Definition: template_lapack_rscl.h:42
logical
bool logical
Definition: template_blas_common.h:41
template_lapack_labad
int template_lapack_labad(Treal *small, Treal *large)
Definition: template_lapack_labad.h:42
TRUE_
#define TRUE_
Definition: template_lapack_common.h:42
integer
int integer
Definition: template_blas_common.h:40
FALSE_
#define FALSE_
Definition: template_lapack_common.h:43